The Old Covenant was a structure, put in place by God, for real, historical interaction with Israel. The law of Moses, in other words, was a kind of legal-covenantal context designed by God for this purpose: to bring his people to greater knowledge of His righteousness and holiness; their wretched, hopeless status before Him; the purely gracious nature of the divine favor they enjoyed; and the promise of final, consummate reconciliation.
So God gave the law in order to teach Israel about holiness, sin, and judgment—and so also about the need for an interposition of divine grace, a ‘rescue plan’ as the children’s Bible puts it.
The law was our guardian until Christ came, in order that we might be justified by faith. But now that faith has come, we are no longer under a guardian, for in Christ Jesus you are all sons of God, through faith (Gal 3:24-6).
The law was, Paul says, “παιδαγωγὸς ἡμῶν.” The phrase is variously translated our ‘instructor’, ‘schoolmaster’, ‘tutor’. The situation is: children guided and trained until they ‘graduate’ or come of age, until they master the content or no longer require the guidance—or until that gracious offer of guidance expires. Those who no longer require this instruction are those who are in Christ Jesus—those for whom the satisfaction of the law by Christ in the flesh has become, by grace through faith, their own satisfaction. They now possess and can never lose a satisfactory death issuing into imperishable life. Having been indwelt with this crucified-and-raised mediator, they no longer need the tutelage of the law.
Objectively speaking, in other words, we may say that the Mosaic law is fulfilled in Christ. It is done away with. So, in a historical, objective sense, the law is fulfilled and Israel’s role in redemptive history has come to an end. In a subjective sense, however, all image-bearers (not only ancient Israelites) live under the condemnation of the law—the unbending righteousness and holiness of God, his unbending standard of perfect holiness—until they are covered by Christ’s death and satisfaction of it.
The Mosaic law, the Old Covenant, was designed to teach all this to ancient Israel through God’s historical response to holiness and to disobedience. The Lord was faithful to His promise to Abraham: he brought Israel, now a great nation, out of slavery and into the land of promise. And when Israel was unfaithful to the terms of the covenant, those very things—their people and their safety and prosperity in the land—were granted experience of the loss of the faithful covenant protection of God: ‘here is what happens if you get what you wish for, independence from God’. In other words: when they disobeyed, the Lord responded and Israel suffered—temporally, as a lesson in what was at stake eternally.
In Acts 17:30 Paul says:
The times of ignorance God overlooked, but now he commands all people everywhere to repent, because he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead.
In my understanding, this tricky phrase ‘times of ignorance’ should be understood within the context of the Mosaic situation, which included two people groups: (1) Israel, being taught, through the law, the righteousness of God and the need for grace, on the one hand; (2) and on the other hand the gentiles—all ‘the nations’. These nations were in the total darkness of suppression and wicked idolatry. They had no redemptive special revelation. (This is a generalization: Israel had the Scriptures, the promises, the covenant, but the gospel of Gen 3:15, having been announced to the ancestors of all peoples, may very well have been preserved and propagated here and there.) So the ‘times of ignorance’ were the times when the promises of God were known only in Israel (Rom 3:2; 9:4-5).
But now the Messiah of God has borne publicly the wrath of God for the sins of the world, and He has been raised—by the Father—so that the Son’s atoning death is the singular, sufficient satisfaction of the righteous wrath of God for all the world. Christ is the end of the law—in the sense that the law particular to Israel, the law of Moses, is not fulfilled in Him. Moses brought the law; Moses gave way to Christ, through whom, in whom, grace and truth are given (John 1:17). Christ Himself is grace and truth. So the Mosaic law is fulfilled, superseded, and ended.
But the ‘law of God’ generally speaking—His moral perfection and sovereignty—can never be superseded in that way. God does not go away; His perfect holiness remains; and creation is always under His full and complete judgment.
So the Mosaic law is a kind of redemptive-historical indicator of the situation of all image-bearers. For a time, only Israel knew this indicator, this guide and tutor. During that time the nations were in ignorance. The Lord did not respond to their wickedness in the way that he responded to the waywardness of Israel. In that sense he overlooked their ignorance. But now the indicator, the hint, the precursor, has been fulfilled, and the tutor has been dismissed. Judgment has been visited in full on the Son. Following upon the resurrection of the Son, the witness of Christ are to make disciples of all nations, teaching them to obey all that He has commanded—first of all, to repent.
There is nothing more relevant to any people anywhere than their state before God. There is nothing more basically relevant to any person anywhere than the need for reconciliation and peace with God, than the gospel of the Son of God.